Pallet conveyance device and substrate inspection device

ABSTRACT

A pallet conveyance device has, besides a mechanism for moving a pallet for supporting a substrate, a lifting mechanism for vertically moving the pallet. The lifting mechanism has an impact cushioning mechanism for cushioning an impact applied to the substrate supported on the pallet. When an impact is applied to the substrate from the pallet, the impact cushioning mechanism controls a vertical motion of the lifting mechanism to cushion the impact applied to the substrate supported on the pallet. The impact cushioning mechanism is a mechanism that changes the drive speed of the lifting mechanism. The impact cushioning mechanism changes the drive speed to a low speed at at least either the start of operation of the lifting mechanism or before the end of the operation, and in a drive period excluding a low speed period, the impact cushioning mechanism changes the drive speed to a high speed.

CROSS REFERENCE TO RELATED APPLICATION

This is a U.S. national phase application under U.S.C. §371 ofInternational Patent Application No. PCT/JP2006/324248 filed Dec. 5,2006. The International Application was published on Jun. 12, 2008 asInternational Publication No. WO/2008/068845 under PCT Article 21(2) thecontents of which are incorporated herein in its entirety.

TECHNICAL FIELD

The present invention relates to a pallet conveyance device that movespallets that support a substrate, and to substrate inspection devicethat contain this pallet conveyance device; and this substrateinspection device can be applied to a liquid crystal substrateinspection device for inspecting liquid crystal substrates used inliquid crystal displays, organic EL displays, and the like.

BACKGROUND OF THE INVENTION

Liquid crystal substrates and thin film transistor array substrates (TFTarray substrate) constitute TFT arrays, in which thin film transistors(TFT) are arranged in a matrix shape on a substrate such as glasssubstrate, and signal electrodes that supply drive signals to these thinfilm transistors; and the thin film transistors are driven by signalsfrom scanning signal electrode terminals and video signal electrodeterminals.

Substrate inspection devices such as TFT array inspection devices andliquid crystal substrate inspection devices are known as devices thatinspect TFT arrays formed on substrate and liquid crystal substrates.Substrate inspection devices are composed of probers and an inspectioncircuit for inspecting the electrical connections of scan signalelectrode terminals and video signal electrode terminals. The inspectioncircuit applies a specified voltage to the inspection probers, detectsthe flow of current caused by that application of voltage, andinvestigates for short circuits between the gate and source, pointdefects, disconnected lines, and the like.

TFT arrays formed on liquid crystal substrate come in a variety of sizesand specifications, differ in layouts, and have differing driveelectrodes formed on the liquid crystal substrate depending on thelayout. For those reasons, substrate inspection devices used to inspectliquid crystal substrate set up the electrode positions of theinspection prober electrodes corresponding to the TFT array layout, andinspections are conducted by substituting these positions correspondingto the liquid crystal substrate to be inspected.

When inspecting liquid crystal substrates, a prober frame is stackedfrom above or below the liquid crystal substrate, the probe pinsprovided on the prober frame make contact with the electrodes of theliquid crystal substrate, and this contact between the probe pins andthe electrodes makes electrical contact between the liquid crystalsubstrate and the prober.

Inspection of semiconductor substrates, which is not limited to theliquid crystal substrate described above, is conducted in an inspectionchamber. To inspect substrate in this inspection chamber, the substrateis mounted on a pallet, this pallet is conveyed from a load lock chamberinto the inspection chamber, and the inspected substrate is dischargedtogether with the pallet.

Pallets can be conveyed between the inspection chamber and the load lockchamber by conveyance rollers provided respectively in the inspectionchamber and the load lock chamber. By providing conveyance rollers inthese chambers, the pallets can be moved in the chambers, and thepallets can be transferred between the inspection chamber and the loadlock chamber.

In order to heighten the efficiency of substrate conveyance in theinspection process, a configuration can be adopted in which severalpallets are arranged up and down in the load lock chamber, and palletsare switched with the conveyance rollers by moving the pallets up anddown.

When moving the pallets up and down to switch the pallets withconveyance rollers, the pallets accelerate when changing from a staticstate to a drive state, or when changing from a drive state to a staticstate. Meanwhile, when a substrate is mounted on a pallet, the substrateis no more than simply placed on the pallet, and therefore, when thepallet is moving, the inertia of the substrate generates a discrepancybetween the movement of the pallet and the movement of the substrate,and the substrate is subjected to impact.

In this kind of configuration, when heightening the velocity of the upand down movement of the pallet in order to quicken the substrateconveyance process and to improve the processing approach of thesubstrates, acceleration of pallets becomes greater. Therefore, thesubstrates are subjected to a greater impact and there is the risk ofsubstrates being damaged by this impact.

Thus, to address the aforementioned problems of the past, an object ofthe present invention is to reduce damage to substrates caused by impactgenerated by pallet drive when conveying substrates using pallets inpallet conveyance devices and in substrate inspection devices containingpallet conveyance devices.

SUMMARY OF THE INVENTION

In addition to a mechanism to move the pallets that support thesubstrate, the pallet conveyance device of the present invention is alsoequipped with a lifting mechanism to move the pallets up and down. Thislifting mechanism is equipped with an impact cushioning mechanism thatcushions the impact to which the substrate that is supported on thepallet is subjected during the lifting operation.

As previously described, when moving a pallet up and down using alifting device, the inertia of the substrate generates a discrepancybetween the movement of the pallet and the movement of the substrate,and may thereby be subjected to impact.

For example, if a pallet on which a substrate is mounted is lifted by alifting mechanism, the velocity of the pallet is decelerated whenstopping the lifting operation, but the velocity of the substratemounted on the pallet is maintained by inertia at that time. For thatreason, the substrate moves in a direction to separate from the pallet,and afterwards lands on the pallet by the force of gravity. Thesubstrate is impacted by the pallet at this time.

Moreover, when the lifting mechanism lowers a pallet on which asubstrate is mounted, the velocity of the pallet is accelerated downwardfrom the stop position, and the substrate mounted on the pallet attemptsto remain stationary at that time by the force of inertia. For thatreason, the substrate temporarily moves toward separation from thepallet, and afterward lands on the pallet by the force of gravity. Atthat time, the substrate is impacted by the pallet.

In operations when the pallet impacts the substrate as described above,the impact cushioning mechanism of the present invention cushions theimpact imparted to the substrate supported on the pallet by controllingthe lifting operation of the lifting mechanism.

The impact cushioning mechanism of the present invention is a mechanismthat switches the drive velocity of the lifting mechanism, switches thedrive velocity of the pallet to low speed after beginning operation andbefore ending operation of the lifting mechanism, and switches the drivevelocity of the pallet to high speed in drive periods other than the lowspeed periods. Here, the periods of switching the pallet drive velocityto low speed are the periods when the velocity changes during start upand termination of the drive operation, and are the periods whenvelocity discrepancies are generated between the pallet and thesubstrate. In this period the extent of velocity change is reduced andthe positional discrepancy between the pallet and substrate is decreasedby decelerating the pallet drive velocity, thereby reducing the impacton the substrate.

For example, during the lifting operation of the lifting mechanism, thelifting operation is begun at the high-speed drive velocity and thedrive velocity is switched to low-speed prior to completing the liftingoperation. By switching and controlling this drive velocity in thelifting operation of the lifting mechanism, the pallet drive velocity isdecreased prior to stopping the lifting operation, and the impactimparted to the substrate when stopping the pallet can be reduced byconducting the stop operation from the low-speed state. Further, whenbeginning the lifting operation, upward facing force acts on thesubstrate from the pallet, and therefore there is little velocitydiscrepancy between the substrate and the pallet and no impact isimparted to the substrate by positional discrepancy between the palletand the substrate.

Meanwhile, during the lowering operation of the lifting mechanism, thelowering operation is begun at the low-speed drive velocity, and thenafter having passed through a specified period from the beginning of thelowering operation, the drive velocity is switched to high-speed. Byswitching and controlling this drive velocity in the lowering operationof the lifting mechanism, the impact imparted to the substrate whenlowering the pallet can be reduced by decelerating the pallet drivevelocity when beginning the lowering operation.

Further, when stopping the lowering operation, upward facing force actsfrom the pallet to the substrate, and therefore there is little velocitydiscrepancy between the substrate and the pallet and no impact isimparted to the substrate by positional discrepancy between the palletand the substrate.

An air cylinder mechanism that is driven by pneumatic pressure is usedas one configuration of the lifting mechanism of the present invention.This impact cushioning mechanism has two compressed air line systems, ahigh-speed compressed air line and a low-speed compressed air line,which supply gas at differing flow rates into the air cylindermechanism.

In these 2 compressed air line systems the flow rate of gas that thelow-speed compressed air line supplies to the air cylinder mechanism isset up to be less than the flow rate of gas that the high-speedcompressed air line supplies to the air cylinder mechanism.

When supplying gas to the air cylinder system using the low-speedcompressed air line, the supply rate of gas supplied to the air cylindermechanism per unit time is small, and therefore the drive velocity ofthe air cylinder mechanism is low-speed, and the movement velocity ofthe pallet that is driven by this air cylinder is low-speed. Meanwhile,when supplying gas to the air cylinder system using the high-speedcompressed air line, the supply rate of gas supplied to the air cylindermechanism per unit time is large compared to that of the low-speedcompressed air line, and therefore the drive velocity of the aircylinder mechanism is high-speed, and the movement velocity of thepallet that is driven by this air cylinder is high-speed.

The lifting mechanism is not limited to the aforementioned air cylindermechanism, and may be a motor-driven mechanism ancillary to the device.In a motor-driven mechanism, for example, adjusting the drive currentcan control the pallet movement velocity.

Moreover, the impact to the substrate is cushioned by switching thepallet drive velocity between high speed and low speed; and the palletconveyance time can be shortened and the substrate conveyance time canbe shortened by switching to high-speed drive.

The lifting mechanism of the present invention can be applied to palletconveyance devices that move multiple pallets supporting substrates. Inthis aspect, the device is composed of the aforementioned liftingmechanism and of a conveyance mechanism that moves one of the multiplepallets horizontally. The lifting mechanism can individually move themultiple pallets up and down or can move and switch a pallet to and fromthe conveyance mechanism, and the pallet is moved and switched by movingup and down and to and from the conveyance mechanism.

Further, the pallet conveyance device of the present invention can beapplied to a substrate inspection device. In the aspect of a substrateinspection device of the present invention, the substrate inspectiondevice is composed of an inspection chamber for inspecting substrates,and a load lock chamber for conveying substrates to and from theinspection chamber; and the load lock chamber constitutes the palletconveyance device of the present invention. The conveyance mechanism iscomposed of a first set of conveyance rollers provided in an inspectionchamber for inspecting substrates, and a second set of conveyancerollers provided in the load lock chamber for conveying substrates inand out of the inspection chamber. The multiple pallets that the liftingmechanism supports in the load lock chamber are conveyed to and from thefirst set of conveyance rollers by sharing the second set of conveyancerollers.

When conveying substrates using pallets, a pallet conveyance deviceaccording to the present invention, and a substrate inspection devicecomposed of this pallet conveyance device, can reduce substrate damagecaused by impact generated by pallet drive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram for explaining a pallet conveyance deviceof the present invention and a substrate inspection device composed ofthis pallet conveyance device;

FIG. 2 is a diagram for explaining an example of the configuration of alifting mechanism of the present invention;

FIG. 3 is a flowchart for explaining the low-speed switching operationwhen operation of the lifting mechanism of the present invention isstopped;

FIGS. 4( a)-4(d) are operational diagrams for explaining low-speedswitching operations while stopping during the lifting operations of thelifting mechanism of the present invention;

FIGS. 5( a)-5(d) are operational diagrams for explaining the low-speedswitching operations while starting during lowering the loweringoperations of the lifting mechanism of the present invention;

FIGS. 6( a)-6(c) are diagrams for explaining the drive of just thehigh-speed line;

FIGS. 7( a)-7(e) are perspective diagrams for explaining an example ofthe operation of the conveyance mechanism and lifting mechanism of thepresent invention;

FIGS. 8( a)-8(c) are cross-sectional diagrams for explaining an exampleof the operation of the conveyance mechanism and lifting mechanism ofthe present invention;

FIGS. 9( a)-9(c) cross-sectional diagrams for explaining an example ofthe operation of the conveyance mechanism and lifting mechanism of thepresent invention;

FIG. 10 is a flowchart for explaining an example of the operation of thepallet conveyance device of the present invention;

FIG. 11 is a flowchart for explaining an example of the operation of thepallet conveyance device of the present invention;

FIGS. 12( a)-12(d) are operational charts for explaining an example ofthe operation of the pallet conveyance device of the present invention;

FIGS. 13( a)-13(d) are operational charts for explaining an example ofthe operation of the pallet conveyance device of the present invention;

FIGS. 14( a)-14(d) are operational charts for explaining an example ofthe operation of the pallet conveyance device of the present invention;

FIGS. 15( a)-15(e) are operational charts for explaining an example ofthe operation of the pallet conveyance device of the present invention;

FIGS. 16( a)-16(d) are operational charts for explaining an example ofthe operation of the pallet conveyance device of the present invention;

FIGS. 17( a)-17(c) are operational charts for explaining an example ofthe operation of the pallet conveyance device of the present invention;

FIGS. 18( a)-18(c) are operational charts for explaining an example ofthe operation of the pallet conveyance device of the present invention;

FIGS. 19( a)-19(c) are operational charts for explaining an example ofthe operation of the pallet conveyance device of the present invention;and

FIGS. 20( a)-20(c) are operational charts for explaining an example ofthe operation of the pallet conveyance device of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Aspects of implementing the present invention will be explained indetail below while referring to the diagrams.

FIG. 1 is a schematic diagram for explaining a pallet conveyance deviceof the present invention and a substrate inspection device composed ofthis pallet conveyance device. Further, part of the configuration of thesubstrate inspection device is also indicated here.

A substrate inspection device 100 is composed of an inspection chamber 3where the introduced substrate (not indicated in the diagram) isinspected, a load lock chamber 2 from which the substrates are conveyedinto and out of the inspection chamber 3, and a gate valve 4 that canfreely seal and open between the inspection chamber 3 and the load lockchamber 2.

The inspection chamber (MC) 3 is a chamber for inspecting semiconductorsubstrate such as liquid crystal substrate, and the substrate, which ismounted on a pallet, is conveyed onto the conveyance rollers 31 insidethe inspection chamber though the gate valve 4. The substrate that hasbeen conveyed into inspection chamber 3 is inspected, and afterinspection has ended, the substrate, which is mounted on a pallet, isconveyed out through the gate valve 4 by the conveyance rollers 31.

An example of the inspection of a liquid crystal substrate conducted inthe inspection chamber will be explained below. Further, theconfiguration to be explained below is not indicated in FIG. 1.

The liquid crystal substrate inspection device is composed of a chargedparticle source that irradiates a charged particle beam on the liquidcrystal substrate targeted for inspection, a detector that detectssecondary electrons emitted from the liquid crystal substrate based onthe irradiation of these charged particles, and other parts such as astage that supports and two-dimensionally scans the liquid crystalsubstrate targeted for inspection; and substrate inspection is conductedbased on scan images obtained by the detector.

The liquid crystal substrate constitutes, for example, a TFT arrayformed on a glass substrate. The layout, electrodes, routing pattern,and the like of the TFT array formed on this liquid crystal substratemay be set up in a variety of ways corresponding to the size of theliquid crystal panel and the specifications. Thin film transistorsformed in a matrix and signal electrode terminals (for example, scansignal electrode terminals, video signal electrode terminals), whichdrive the thin film transistors, are formed in the TFT array on theliquid crystal substrate. Moreover, an electrode is formed outside ofthe array on the liquid crystal substrate for electrically connectingwith a unit exterior to the liquid crystal substrate.

In addition, the liquid crystal substrate inspection device is composedof a prober (not indicated in the diagram) that supplies inspectionsignals to the liquid crystal substrate. The prober is composed of aprober frame (not indicated in the diagram) for electrically connectingwith the electrodes of the liquid crystal substrate and conductinginspections, and of probe pins (not indicated in the diagram) forelectrically connecting with the electrodes of the liquid crystalsubstrate.

In order to inspect the liquid crystal substrate, the probe frame isarranged on the liquid crystal substrate that is mounted on a pallet.The probe pins coming into contact with the electrodes make anelectrical connection between the liquid crystal substrate and theprober frame, and inspection signals are supplied to the TFT arraythrough the connection between the probe pins and the electrodes.Moreover, the connection between the prober framer and the pallet orstage is made by a connector (not indicated in the diagram) provided onthe prober frame and the pallet.

Further, the pallet can move freely by being mounted on a stage (notindicated in the diagram). The electrical connection between the palletand the stage can be made by a pallet-side connector provide on thepallet and a stage-side connector provided on the stage side.

The inspection device and the conveyance rollers 31 provided inside theinspection chamber 3 are controlled by an inspection device control unit43, which is controlled by a control unit 40.

The load lock chamber 2 is a chamber where substrates are introducedfrom the outside, substrates mounted on a pallet are conveyed into theinspection chamber 3, inspected substrates mounted on pallets areconveyed out from the inspection chamber 3, and the substrates arereturned to the outside; and load lock chamber 2 has a configuration inwhich multiple pallets can be arranged up and down in order toefficiently convey substrates in and out of the inspection chamber 3.

A pallet conveyance device 1, which moves the multiple palletshorizontally as well as up and down, is provided inside the load lockchamber 2. This pallet conveyance device 1 is composed of a conveyancemechanism 10, which has a set of conveyance rollers 11 that movespallets horizontally and conveys pallets in and out of the inspectionchamber 3, and a lifting mechanism 20 that moves and switches palletswith the conveyance rollers 11 by moving pallets up and down.

The conveyance rollers 11 of the conveyance mechanism 10 constitute amechanism that moves pallets horizontally in the load lock chamber 2,and conduct operations to introduce and discharge substrates between theload lock chamber 2 and the outside, and operations to convey substratesin and out of the inspection chamber 3. This conveyance mechanism 10 iscontrolled by a conveyance roller control unit 41 that is controlled bya control unit 40.

The lifting mechanism 20 is provided above and below with multiplepallet support parts 22A, 22B that support pallets, and is driven by anair cylinder mechanism (not indicated in FIG. 1) by pneumatic pressure.The air cylinder mechanism of this lifting mechanism switches liftingvelocities using an impact cushioning mechanism 24. Switching liftingvelocities using this impact cushioning mechanism 24 is conducted byswitching the flow rate of gas supplied to the air cylinder. Thislifting mechanism 20 is controlled by controlling the impact cushioningmechanism 24 using a lifting mechanism control unit 42 that iscontrolled by the control unit 40.

Moreover, the gate valve 4, which opens and closes between the load lockchamber 2 and the inspection chamber 3 is controlled by a valve controlunit 44 that is controlled by the control unit 40.

An example of a configuration of the lifting mechanism 20 will beexplained using FIG. 2. Further, one of the multiple pallet supportparts 22 provided in the lifting mechanism 20 is indicated in FIG. 2.

The lifting mechanism 20 is composed of multiple pallet support parts 22that support a pallet and a mount 21 that maintains the aforementionedpallet support parts 22 for being driven up and down. The air cylinder23 freely moves the mount 21 up and down.

This air cylinder drives by being supplied gas from a gas supply source(not indicated in the diagram) through the impact cushioning mechanism24. The impact cushioning mechanism 24 is composed of a high-speedcompressed air control circuit 24 a, which configures a high-speed line,and a low-speed compressed air control circuit 24 b, which configures alow-speed line; and the lifting velocities of the mount 21 and thepallet support parts 22 are controlled by switching between thehigh-speed line and the low-speed line.

The high-speed compressed air control circuit 24 a is configured by alinear connection of a electromagnetic valve 25 a and a flow rateadjuster 26 a, while the low-speed compressed air control circuit 24 bis configured by a linear connection of a electromagnetic valve 25 b anda flow rate adjuster 26 b.

One or the other of the high-speed line or the low-speed line isconnected to the air cylinder 23 by exclusively switching between theelectromagnetic valve 25 a and the electromagnetic valve 25 b. The flowrate regulator 26 a and the flow rate regulator 26 b regulate the flowrate of the gas supplied to the air cylinder 23. The flow rate regulator26 a of the high-speed compressed air control circuit 24 a regulates theflow rate such that more gas is supplied than with the flow rateregulator 26 b of the low-speed compressed air control circuit 24 b. Theair cylinder 23 drives at a speed corresponding to the flow rate set upby the flow rate regulator 26 a or the flow rate regulator 26 b.

Further, the configuration of the lifting mechanism 20 indicated in FIG.2 indicates that the air cylinder 23 has mainly been driven upward bythe compressed air supplied by the high-speed line or the low-speedline.

Meanwhile, the air cylinder 23 can be driven downward by reducing thepressure in the air cylinder 23, and the lowering velocity can becontrolled by adjusting the flow rate by which gas inside the cylinder23 is suctioned. The suctioning flow rate can be regulated by connectinga suction pump through the linear connection of the electromagneticvalve and the flow rate regulator in the same way as the impactcushioning mechanism 24. In this case as well, a high-speed line and alow-speed line with differing flow rates based on regulation by flowrate regulators are provided, and the downward drive velocity of the aircylinder 23 can be switched by exclusively selecting the high-speed lineor the low-speed line.

Next, the operation of the impact cushioning mechanism will be explainedusing FIG. 3 through FIG. 6.

FIG. 3 is a flowchart of the low-speed switching operation whenoperation of the cylinder is being stopped, and FIG. 4 is an example oflow-speed switching operations when operation of the cylinder is beingstopped. This example is applicable to impact cushioning when raising apallet. An example of the operation when raising a pallet will bedescribed below.

When raising begins (S1), the air cylinder 23 is driven from the lowposition of the mount 21 by the high-speed line (A in FIG. 4( a)), andthe mount 21 rises at high speed (B in FIG. 4( c)). Operation of thehigh-speed line is conducted by leaving the electromagnetic valve 25 bof the low-speed compressed air control circuit 24 b shut, and releasingthe electromagnetic valve 25 a of the high-speed compressed air controlcircuit 24 a thereby supplying gas (for example, air) into the aircylinder 23 at a high flow rate (S2).

As this mount 21 begins to rise, the pallet accelerates rapidly (C inFIG. 4( d)), but no positional discrepancy between the pallet and thepallet support part is generated because this acceleration works in thedirection of pushing the pallet onto the pallet support part.

Immediately before stopping the air cylinder 23 (S3), the air cylinder23 is driven by switching from the high-speed line to the low-speed line(D in FIG. 4( b)), and the mount 21 is switched to low-speed (E in FIG.4( c)). Operation of the low speed line is conducted by closing theelectromagnetic valve 25 a of the high-speed compressed air controlcircuit 24 a, opening the electromagnetic valve 25 b of the low-speedcompressed air control circuit 24 b, and lowering the flow rate of gas(for example, air) supplied to the air cylinder 23 (S4).

When stopping the mount 21, the velocity of the pallet support part islower than that of the pallet mounted thereon, which attempts tomaintain velocity through inertia, and therefore that lower velocityoperates in a direction to create a positional discrepancy between thepallet and the pallet support part. By switching to this low-speed line,however, the force operating to make the pallet float up from the palletsupport part becomes small compared to the force of gravity, and nopositional discrepancy is generated between the pallet and the palletsupport part.

When lifting reaches the end position (S5), the electromagnetic valve 25b of the low-speed line is closed, and the gas supply to the aircylinder 23 is stopped (S6).

FIG. 5 is an example of the operation of switching to low speed whenbeginning operation of the cylinder, and can be applied to cushioningimpact when lowering the pallet. An example of the operation to lowerpallets will be explained below.

When lowering pallets, with the mount 21 in the upper position, the aircylinder 23 is driven by the low-speed line (G in FIG. 5( a)), and themount 21 is lowered at low speed (H in FIG. 5( c)). Operation of thelow-speed line is conducted by leaving the electromagnetic valve 25 a ofthe high-speed compressed air control circuit 24 a shut, and releasingthe electromagnetic valve 25 b of the low-speed compressed air controlcircuit 24 b thereby limiting the flow rate of gas into the air cylinder23.

When beginning to lower mount 21, the mount operates in a direction tocreate a positional discrepancy between the pallet and the palletsupport part. However, the pallet accelerates slowly (I in FIG. 5( d)),and the force operating to cause the pallet to fly up from the palletsupport part is small compared to the force of gravity, and therefore,no positional discrepancy is generated between the pallet and the palletsupport part.

After the air cylinder 23 begins to descend, the air cylinder is drivenby switching from the low-speed line to the high-speed line (J in FIG.5( a)), and the mount 21 is switched to high speed (K in FIG. 5( c)).Operation of the high-speed line is conducted by closing theelectromagnetic valve 25 b of the low-speed compressed air controlcircuit 24 b, opening the electromagnetic valve 25 a of the high-speedcompressed air control circuit 24 a, and increasing the flow rate of gas(for example, air) supplied into the air cylinder 23.

When stopping the mount 21 (M in FIG. 5( a)), the velocity of the palletsupport part is lowered in relation to that of the pallet mountedthereon, which attempts to maintain velocity through inertia (N in FIG.5( c)). That acceleration operates in a direction to press the palletonto the pallet support part (O in FIG. 5( d)), and therefore nopositional discrepancy is generated between the pallet and the palletsupport part.

FIG. 6 is a diagram for explaining the drive of just the high-speed linewithout using the impact cushioning mechanism to switch between thehigh-speed line and the low-speed line.

With the mount 21 in the low position, the air cylinder 23 is driven bythe high-speed line (P in FIG. 6( a)), and the mount 21 is driven athigh speed (Q in FIG. 6( b)). When beginning to drive this mount 21, thepallet is accelerated rapidly (R in FIG. 6( c)). In addition, whenstopping the air cylinder 23 (S in FIG. 6( a) and T in FIG. 6( b)), thepallet is also accelerated rapidly (U in FIG. 6( c)).

As described above, when driven only by the high-speed line, the palletundergoes great acceleration when beginning drive and when stoppingdrive. If the direction of this acceleration is opposite to thedirection of gravity, the substrate mounted on the pallet moves in adirection of separation from the pallet because of inertia, and apositional discrepancy may be generated between the pallet and thepallet support part.

In contrast, as indicated in FIG. 4 and FIG. 5, the acceleration towhich the pallet is subjected is decreased by switching to the low-speedline, and even if the substrate mounted on the pallet moves in thedirection of separation because of inertia, no positional discrepancybetween the pallet and the pallet support part is generated.

Next, in an operational example of the conveyance mechanism 10 and thelifting mechanism 20, the operation of placing a pallet on theconveyance rollers after having been lifted by the lifting mechanism 20will be explained using FIG. 7 to FIG. 9. Further, FIG. 7 is aperspective drawing, and FIG. 8 and FIG. 9 are cross-sectional diagrams.

Initially, let the pallet support parts 22 be positioned below theconveyance rollers 11, and let a pallet 50 be supported on these palletsupports 22. At this time, the space between the conveyance rollers 11on the two sides is the distance at which pallet 50 is placed (FIG. 7(a), FIG. 8( a)). Because the space between the conveyance rollers 11 onthe two sides is the distance at which pallet 50 is placed, if thepallet 50, which is supported on the pallet support parts 22, is liftedby the lifting mechanism 20 in this state, the pallet 50 will bump intothe conveyance rollers 11. Therefore, pallet 50 cannot be placed on theconveyance rollers 11.

Thus, the conveyance rollers 11 are moved to the outside, broadening thespace between the rollers, such that the pallet support parts 22 and thepallet 50 can pass between the rollers (FIG. 7( b), FIG. 8( b)). Afterthe distance between the rollers has been widened, the pallet supportparts 22 are raised by the lifting mechanism 20 and pass between therollers, and the pallet 50 is moved to a position above the conveyancerollers 11 (FIG. 7( c), FIG. 8( c)). After the pallet support parts 22and the pallet 50 have been moved to a position above the conveyancerollers 11, the space between the roller is narrowed by moving theconveyance rollers 11 to the inside, setting up a space at which thepallet 50 can be placed on the conveyance rollers 11 (FIG. 7( d), FIG.9( a)). Afterwards, the pallet support parts 22 are lowered, and thepallet 50 is placed on the conveyance rollers 11 (FIG. 7( e), FIG. 9(b)). After the pallet 50 is supported on the conveyance rollers 11, thepallet support parts 22 can be lowered further, and the pallet 50 can beconveyed by the conveyance rollers 11 (FIG. 9( c)).

Next, an example of the operation of a pallet conveyance device of thepresent invention will be explained using the flowcharts in FIG. 10 andFIG. 11, and the operational explanatory diagrams in FIG. 12 to FIG. 20.

In one embodiment the conveyance device 10 in the load lock chamber 2 isprovided with one set of conveyance rollers 11, two pallets are housedpositioned above and below, and pallet switching is conducted to andfrom conveyance rollers 11. Moreover, as the initial state, assume thatinside the 2 pallet support parts provided inside the load lock chambertwo the upper pallet 50 u is supported on the upper pallet support part,no pallet is supported on the lower pallet support part, nor is a pallethoused inside the inspection chamber 3. Further, assume that the upperpallet 50 u is positioned above the conveyance rollers 11.

Initially, the upper pallet 50 u is lowered by driving the liftingmechanism 20, and the substrate 60 to be supported is placed on theupper pallet 50 u (S11) (FIG. 12( a)). Gate valve 4 is opened, theconveyance rollers 11 are driven, and the upper pallet 50 u mounted onthe conveyance rollers 11 is conveyed from the load lock chamber 2 intothe inspection chamber 3. At that time, the lower pallet 50 d issupported in a position below the conveyance rollers 11 (S12) (FIG. 12(b)).

After the upper pallet 50 u has been conveyed into the inspectionchamber 3, the gate valve 4 is closed, and the substrate 60 mounted onthe upper pallet 50 u is inspected inside the inspection chamber 3 (S13)(FIG. 12( c), FIG. 17( a)).

While substrate inspection is being conducted in the inspection chamber3, on the load lock chamber 2 side preparations are being conducted toconvey the lower pallet 50 d into the inspection chamber 3.

In the load lock chamber 2 the rollers of the conveyance rollers 11 aremoved to the outside to widen the distance between rollers so that thelower pallet 50 d can be moved upward between the rollers of theconveyance rollers 11 (S14) (FIG. 17( b)). The lower pallet 50 d israised and passed through the spread rollers of the conveyance rollers11 (S15) (FIG. 12( d), FIG. 17( c)).

A substrate targeted for inspection is introduced from the outside, andis placed on the lower pallet 50 d that has been raised above theconveyance rollers 11 (S16) (FIG. 13( a), FIGS. 18( a), (b)).

After substrate inspection has been completed in the inspection chamber3, the gate valve 4 is opened, the upper pallet 50 u is conveyed fromthe inspection chamber 3 to load lock chamber 2 through this gate valve4 (S17) (FIG. 13( b), FIG. 18( c)). After the upper pallet 50 u that hasbeen conveyed out has been moved onto the conveyance rollers 11 in theload lock chamber 2, the gate valve 4 is closed (S18) (FIG. 13( c)).

The upper pallet 50 u is moved and switched onto the conveyance rollers11. The moving and switching onto the conveyance rollers 11 can beconducted by supporting the upper pallet 50 u using the pallet supportpart (FIGS. 19( a), (b)), and then moving the rollers outward (FIG. 19(c)).

After the upper pallet 50 u has been lowered through the opened rollers(S19) (FIG. 20( a)), the rollers of the conveyance rollers 11 are movedto the inside (S20) (FIG. 20( b)), the lower pallet 50 d is lowered andplaced on the conveyance rollers 11 (S21) (FIG. 13( d), FIG. 20( b)).

The gate valve 4 is opened, and the lower pallet 50 d is conveyed intothe inspection chamber 3 through this gate valve 4 (S22) (FIG. 14( a),FIG. 20( c)). After the lower pallet 50 d has been conveyed into theinspection chamber 3, the substrate is inspected inside the inspectionchamber 3 (S23) (FIG. 14( b)).

While the substrate mounted on the lower pallet 50 d is being inspectedin the inspection chamber 3, in the load lock chamber 2, the upperpallet 50 u is raised (FIG. 14( c)), and the inspected substrate mountedon the upper pallet 50 u is discharged (S25) (FIG. 14( d)). A substratetargeted for inspection is introduced and placed on the upper pallet 50u (S26) (FIG. 15( a)).

Moving the rollers of the conveyance rollers 11 on the load lock chamber2 side to the outside to widen the distance between rollers makes itpossible for the upper pallet 50 u to move up and down through therollers of the conveyance rollers 11 by (S27). The upper pallet 50 u isthen lowered and passed through the spread rollers of the conveyancerollers 11 (S28) (FIG. 15( b)).

Gate valve 4 is opened, the lower pallet 50 d in the inspection chamber3 is conveyed out from the inspection chamber 3 into the load lockchamber 2 (S29) (FIG. 15( c)), and gate valve 4 is closed (S30) (FIG.15( d)). The lower pallet 50 d is raised by the lifting mechanism 20 onthe load lock chamber 2 side (FIG. 16( a)), and the inspected substrateis discharged to the outside (FIG. 16( b)) (S31). A substrate targetedfor inspection is introduced and placed on the lower pallet 50 d (S32)(FIGS. 16( c)), (d)).

Further, in the example of the above configuration, an air cylindermechanism was used as the lifting mechanism, but the present inventionis not limited to an air cylinder mechanism. A mechanism driven by amotor ancillary to the conveyance device may also be used, and switchingthe pallet movement velocity between high-speed and low-speed may becontrolled by regulating the drive current.

The pallet conveyance device of the present invention is not limited toconveyance of liquid crystal substrates, and can be applied toconveyance of semiconductor substrates.

The substrate inspection device of the present invention is not limitedto inspection of liquid crystal substrates, and can be applied toinspection of semiconductor substrates.

1. A pallet conveyance device for moving a pallet that supports a substrate comprising: a lifting mechanism moving the pallet up and down; and comprises: an impact cushioning device cushioning an impact imparted to the substrate supported on the pallet during operation of the lifting mechanism, wherein the impact cushioning mechanism controls the operation of the lifting mechanism.
 2. The pallet conveyance device according to claim 1, wherein the impact cushioning mechanism switches a drive velocity of said lifting mechanism; wherein the drive velocity is switched to low speed either when beginning operation of said lifting mechanism or slightly before completing operation; and wherein the drive velocity is switched to high-speed in drive periods other than said low-speed periods.
 3. The pallet conveyance device according to claim 2, wherein during a raising operation of the lifting mechanism, the lifting operation is begun at the high-speed drive velocity, and the drive velocity at a specified period prior to completing the raising operation is switched to low-speed; and during a lowering operation of the lifting mechanism, the lowering operation is begun at the low-speed drive velocity, and after a specified period has passed after lowering has begun the drive velocity is switched to high-speed.
 4. The pallet conveyance device according to claim 2, wherein the lifting mechanism is an air cylinder mechanism that drives using pneumatic pressure; wherein the impact cushioning mechanism has two compressed air line systems comprising a high-speed compressed air line and a low-speed compressed air line for supplying gas at differing flow rates to the air cylinder mechanism; wherein a specified period, the air cylinder mechanism is driven at low speed by using the low-speed compressed air line to reduce the supply volume of gas per unit time supplied to said air cylinder mechanism; and wherein the drive period other than the specified period, the air cylinder mechanism is driven at high speed by using the high-speed compressed air line to increase the supply volume of gas per unit time supplied to said air cylinder mechanism.
 5. The pallet conveyance device according to claim 1 further comprising: a conveyance mechanism that moves one pallet of a plurality of pallets horizontally, and wherein the lifting mechanism can move and switch the pallet to and from the conveyance mechanism, and the pallet is moved and switched by moving up and down and to and from said conveyance mechanism.
 6. The pallot conveyance device according to claim 5, further comprising, an inspection chamber for inspecting substrates, and a load lock chamber for conveying substrates to and from the inspection chamber; wherein the conveyance mechanism comprises a first set of conveyance rollers provided in the inspection chamber for inspecting substrates, and a second set of conveyance rollers provided in the load lock chamber for conveying substrates in and out of the inspection chamber, and the plurality of pallets that the lifting mechanism supports in the load lock chamber are conveyed to and from the first set of conveyance rollers by sharing said second set of conveyance rollers. 